Devices for measuring the amount of fuel remaining in a vehicle fuel tank are well known in the automobile industry. A frequent problem facing such devices is that the fuel tank is constantly subject to tilt, such as when the vehicle is accelerating, braking, cornering, or absorbing shock from the roadways over which it travels. Thus, the surface of the fuel in the tank is constantly jostled, and any instantaneous measurement of the amount of fuel in the tank contains some degree of error.
One approach to this problem has been the use of averaging, whereby several measurements are taken over time, and then averaged to obtain an approximate fuel level reading. For example, U.S. Pat. No. 4,402,048 to Tsuchida et al., issued Aug. 30, 1983, discloses a method and apparatus for sampling the amount of fuel over time, eliminating any abnormal values detected which might correspond to changes in attitude of the vehicle, and computing the average fuel level from the remaining values. U.S. Pat. No. 4,470,296 to Kobayashi et al., issued Sept. 11, 1984, teaches a variation of the averaging technique whereby the sampling times over which fuel measurements are taken are increased when the fuel is unstable.
A drawback to averaging, however, is that it is imprecise. By definition, averaging techniques and devices calculate a value from a set of disparate measurements, and thus do not give the actual amount of fuel remaining in the tank.
Accordingly, it is an object of the invention to provide a fuel level gauging apparatus which will improve fuel gauge accuracy.
Another object of the invention is to provide a fuel level gauging apparatus which updates the display indicating the amount of fuel remaining only if the vehicle is tilted less than a predetermined value.
Another object of the invention is to provide a fuel level gauging apparatus which updates the display indicating the amount of fuel remaining only if the vehicle is substantially level and not accelerating or decelerating.
Another object of the invention is to provide a fuel level gauging apparatus which updates the display with a corrected signal which is calculated by applying a correction factor corresponding to the degree to which the fuel tank is askew to a reference plane to a signal received from a fuel remaining sensor.
A more specific object of the invention is to provide a fuel level gauging apparatus which updates the fuel display at least twice per minute.
Another specific object of the invention is to provide a method of gauging an amount of liquid fuel remaining in a vehicle fuel tank which improves fuel gauge accuracy.